The present invention relates to a color gamut displaying method, an image processing method, and an apparatus capable of utilizing the methods, which are suitable for a color management system, and the like, for instance, reproducing colors faithfully in consideration with characteristics of a color input/output device.
As shown in FIG. 32, color ranges which can be reproduced by devices, such as a scanner, a monitor, and a printer, are different each other.
In FIG. 32, x and y denotes axes for chromaticity, and insides of closed areas are color gamuts. In other words, the key to reproduce colors after considering the difference in a color gamut is how to deal with portions of ranges which are not common to different devices. For example, when transformation from a monitor color space to a printer color space is considered, a major problem is that which color should be used to express a color outside of a color gamut of a printer. A process to deal with the above-said problem is called a color gamut compression process.
A color management system has major functions, such as a function of performing the color gamut compression process for faithfully reproducing colors in consideration with characteristics of a color input/output device, as well as a color gamut checking function for checking whether or not it is possible to reproduce a color by an output device. The latter function is used to determine whether or not color data, included in an application software and the like, can be reproduced by an output device (e.g., printer monitor).
Specifically, a method which is shown in FIG. 34 is suggested by the present inventor.
According to the method, a color gamut of a printer is defined by a color reproduction solid whose shape is a hexahedron, determined by peaks of red, green, blue, cyan, magenta, yellow, white, and black. Then each surface of the hexahedron is divided into two triangles to obtain total of twelve areas. Finally, image data is determined whether it is inside or outside of the areas, thereby it is determined if the image data is in the color gamut or not.
However, there are problems to be solved in the aforesaid method.
(1) A real color gamut of a printer has a three dimensional solid which is too complicated to express with a hexahedron, thus the precision of checking the color gamut is low.
(2) It is not a simple process to determine whether or not image data is inside of the twelve areas, thus it requires a long time to complete the process.
The present invention has been made in consideration of the above situation, and has as its object to provide a color gamut expression method for realizing a color gamut checking function which improves the precision of checking and shortens a processing time in a color management system and the like.
Further, another object of the present invention is to provide an image processing method and an apparatus utilizing the method, capable of converting input image data into image data which enables to reproduce inputted image data more faithfully by a color reproduction device.
Especially, it is an object to provide an image processing method and apparatus which are most suitable for a checking function which checks input image data and a color gamut of a printer, and which reproduce colors designated by the input image data more faithfully.
The foregoing object is attained by providing an apparatus, where the color gamut is defined by a solid in a three dimensional space, comprising color gamut expression means for expressing defined color gamut by combinations of color gamut data on the basis of a second and a third axes extending to both the positive and negative directions on a plane perpendicular to a first axis of the three dimensional space and coordinates of the first axis.
Further, the foregoing object is attained by providing an apparatus comprising processing means which defines a color gamut by a solid in a three dimensional space, and determines the color gamut of the color reproduction device by combinations of color gamut data on the basis of second and third axes extending to both the positive and negative directions on a plane perpendicular to a first axis of the three dimensional space and coordinates of the first axis, and processes an input color image data depending upon whether or not the input color image data is within the determined color gamut.
Furthermore, the foregoing object is attained by providing an apparatus comprising storage means for storing information on a defined color gamut expressed by combinations of color gamut data on the basis of second and third axes extending to both the positive and negative directions ona plane perpendicular to a first axis of a three dimensional space where a color gamut of a color reproduction device is defined as a solid and coordinates of the first axis, determination means for determining whether or not input image data is within the defined color gamut on the basis of the information stored in the storage means, and image processing means for processing the input image data on the basis of the result of determination means.
According to a constitution as described above, there can be provided an image processing method capable of converting input image data into image data which enables to reproduce inputted image data more faithfully by a color reproduction device.
Further, the color gamut for realizing the color gamut checking function is easily confirmed, the precision of determining the color gamut can be improved, as well as the time to process the color reproduction can be shortened.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.